Plural base transistor structure and circuit



June 5, 1962 J. LUSCHER PLURAL BASE TRANSISTOR STRUCTURE AND cmcun Filed Dec. 24; 1958 FIG. 2

s 5 9.. a, b b 6 USCHER INVENTOR JAKOB L ATTORNEY United States Patent 3,038,087 PLURAL BASE TRANSISTOR STRUCTURE AND CIRCUIT The present invention relates to a transistor comprising three layers constituting, respectively, the base, the emitter and the collector, each of the latter two being provided with an electrode to enable it to be connected to an electric circuit.

The transistor according to the invention is distinguished from known transistors by the fact that the said base is provided with two electrodes situated at different distances from the emittter, so that it is possible to connect the base to two independent electric circuits permitting of controlling the emitter current, means being provided for varying within wide limits, by means of the space charge zone due to the potential difference between the collector and the base, the electric resistance of that part of the base by means of which one of its electrodes is electrically connected to the emitter-base junction, without substantially modifying the resistance of that part of the base by which the other of its electrodes is electrically connected to the said junction.

A number of constructional forms of the subject of the invention are diagrammatically illustrated by way of example in the accompanying drawings.

FIG. 1 is a view of a transistor according to a first constructional form, as seen from the emitter side.

FIG. 2 is a section along the line 11-11 of FIG. 1.

FIGS. 3 to 5 show in section three other constructional forms.

FIG. 6 is a diagram of the application of the transistor.

As will be seen from FIG. 2, the transistor comprises in the usual manner a central semi-conductor layer, for example of n-type, which is intended to form the base B. Provided on either side of the base B by any of the known methods-for example by the alloying processis a p-type semi-conductor layer intended to form the emitter E and the collector C respectively. Each of the said three layers B, E and C is provided with an electrode b, e, and 0 respectively by means of which it can be con nected to an electric circuit. The electrode b is in the form of a ring surrounding the emitter E.

Formed in the base B on the emitter side, between the said emitter E and the electrode b, is a circular groove 0 surrounding the emitter. At its part B situatedbetween the groove 0 and the emitter E, the base is provided with a second electrode 11,, also in the form of a ring.

The electrodes b and b, may be connected to different electric circuits, and the emitter current may therefore be controlled by two different control voltages. In addition, the electric resistance of that part of the base B which electrically connects the electrode b to the emitterbase junction may be varied by the voltage of the collector C within such limits that the control circuit of which it forms part can be substantially interrupted.

Since the space charge zone due to the potential difference between the collector and the base is proportional to the square root of the collector voltage for a given base, the latter voltage may be made such that this zone extends as far as the groove 0, as indicated in chain lines in FIG. 2, and substantially breaks the circuit b-E. Since the part B of the base is not reached by the said zone, its resistance remains substantially unchanged, so

' Patented June 5, 1962 that the control circuit of which itforms part can always be utilised.

The possibilities of such a transistor are much greater than those of a known transistor.

Thus, for example, in order to provide a bistable multivibrator with the aid of the transistors generally employed, it is necessary to use two of these elements. These two transistors, which are connected in accordance with the known circuit diagrams, must alternately conduct and block a current, depending upon the polarity of the pulses of the control voltage. Since the conductive state of only one element is generally utilised, the current resulting from the conductive state of the other element represents a loss. Now, this is a great disadvantage in the case of circuit arrangements utilising a very large number of multivibrators, such as, for example, those in computing machines or in electronic counters. Another disadvantage obviously resides in the fact that two transistors are required to each multivibrator.

Now, a single transistor according to the invention, as hereinafter described, can be used as a bistable multiifator, for example in accordance with the diagram of As will be seen, the collector C is connected through a resistance R to the negative pole of a direct-voltage source S. The positive pole of the source S is connected to the emitter E, which is earthed. The electrode b is negatively biased in relation to the emitter E by means of a source S The electrode b is positively biased in relation to the emitter E by means of a source S which is effected through a resistance R On the other hand, the electrode b, is connected through a capacitor K to an alternating-voltage pulse generator I.

When no pulse is sent from the generator I to the electrode b,, with the base B subjected to a negative voltage through electrode b, the transistor is in the conductive state. Since the voltage drop across the resistance R is very slightly lower than the voltage of the source S, the voltage of the collector C is therefore very low. If then a positive voltage pulse is emitted from the generator I to the part B of the base through the electrode b the transistor will be momentarily blocked. This will produce an increase in the voltage of the collector C to the value of the voltage of the source S. As the value of the latter is so chosen that the space charge Z0118 due to the potential difference between the collector and the base can extend as far as the groove 0 (shown in chain lines in the drawing), the value of the electric resistance of that part of the base which electrically connects the electrode b to the emitter-base junction will be practically infinite, so that the circuit bE will be practically interrupted. Owing to the positive biasing of the electrode b by the source 8,, the transistor will remain blocked even when the cause of the blocking, namely the positive voltage, has ceased. It will remain blocked until a negative voltage pulse, supplied by the generator I, is applied to the part 13 of the base through the electrode b so as to repel the space charge zone due to the potential difference between the collector and the base, thus reducing the resistance of that part of the base which connects b and E and restoring the interrupted circuit. The transistor is therefore again in a conductive state and it will remain so until a further positive pulse is supplied by the generator I. The transistor will therefiore function as a bistable multivibrator.

It is to be noted that it is not necessary, in order to obtain the above-described operation, to extend the space charge zone as far as the groove 0, that is, to increase the resistance of that part of the base which electrically connects the electrode b to the emitter-base junction to a practically infinite value. It is in fact sufficient to increase this resistance 'to a value at which the etfect of the negative biasing by the source S on the control of the emitter current is negligible in relation to the elfect of the positive biasing by the source 8,.

FIGS. 3 to 5 show three other constructional forms of the transistor according to the invention.

In the constructional form illustrated in FIG. 3, the base 3 comprises a thickened portion B on which are disposed the emitter E and the electrode b It will readily be seen that the electric resistance of that part of the base which electrically connects the electrode b to the emitterbase junction can be varied by means of the space charge zone due to the potential difference between the collector and the base without modifying the resistance of that part B, which connects the electrode b; to the said junction.

The transistor according to FIG. 4 comprises two ringshaped auxiliary collectors C and C one on either side of the base, and situated between the electrode b and b, of the base. These auxiliary collectors C and C are electrically connected to the main collector C. The electric resistance of that part of the base'which connects the electrode b to the emitter-base junction can here be varied by the space charge zones due to the potential differences between each of the auxiliary collectors and the base, which zones may extend one towards the other and even be joined together, without modifying the resistance of the part B connecting the electrode b, to the said junction.

In the transistor illustrated in FIG. 5, a part of the layer constituting the base B, notably the part B on which the emitter and the electrode b are positioned, has a greater impurity content than the remainder of the base B. In this case, the electric resistance of that part of the base which is of lower impurity content and which connects the electrode b to the emitter-base junction may be varied by the space charge zone due to the potential difference between the collector and the base without the resistance of that part B of the base which has higher impurity content and which connects the electrode b; to said junction being substantially modified.

In the constructional forms described and illustrated by way of example, the two electrodes b and b of the base are ring-shaped. It is obvious that they could have any other form. I

It will be understood that the invention is not limited to the embodiments described and illustrated by way of example. Any other embodiment or variant having the essential features of the present invention must be regarded as forming part thereof.

What I claim is:

1. A transistor comprising a base, an emitter, collector means including a collector, said emitter and collector means being provided with electrodes for connection in an electric circuit and said emitter and the collector of said means being mounted in opposed positions on opposite sides of said base, and a pair of base electrodes for connecting said base to a pair of independent electric circuits for controlling the emitter current, said base interconnecting in electrically conductive relation said base electrodes with said emitter and having on the emitter side of the base a portion opposite said collector supporting one of said base electrodes and the emitter, and said base having a region adjacent to said collector means electrically between said other electrode of the base and said emitter for said region to accommodate space charge produced in response to application of a predetermined potential to said collector means thus altering the electrical resistance of said region, said portion of the base having a face extending from the emitter side of the base to said region of the base at a locus from the emitter between said one base electrode and said other base electrode, and said portion being substantially isolated electrically from said other base electrode when said face is contacted by space charge in said region and being of such extent from said region that electrical conductivity is substantially unaltered between said one electrode of the base and the emitter.

2. A transistor comprising a base, an emitter and a collector mounted in opposed positions with respect to each other on opposite sides of said base and provided with electrodes for connection in an electric circuit, and a pair of base electrodes for connecting said base to a pair of independent electric circuits for controlling the emitter current, said base interconnecting in electrically conductive relation said base electrodes with said emitter and having on the emitter side of the base a portion opposite said collector supporting one of said base electrodes and the emit-ter, and said base having a region adjacent to said collector electrically between said other electrode of the base and said emitter for said region to accommodate space charge produced in response to application of a predetermined potential to said collector thus altering the electrical resistance of said region, said portion of the base being adjacent to a groove in said base extending from the emitter side of the base to said region of the base at a locus firom the emitter between said one base electrode and said other base electrode, and said portion being substantially isolated electrically from said other base electrode when said groove is contacted by space charge in said region and being of such extent outward from said region that electrical conductivity is substantially unaltered between said one electrode of the base and the emitter.

3. A transistor comprising a base, an emitter and a collector mounted in opposed positions with respect to each other on opposite sides of said base and provided with electrodes for connection in an electric circuit, and a pair of base electrodes for connecting said base to a pair of independent electric circuits for controlling the emitter current, said base interconnecting in electrically conductive relation said base electrodes with said emittter and having on the emitter side of the base a thickening portion opposite said collector supporting one of said base electrodes and the emitter, and said base having a region adjacent to said collector electrically between said other electrode of the base and said emitter for said region to accommodate space charge produced in response to application of a predetermined potential to said collector thus altering the electrical resistance of said region, said thickening portion of the basehaving a face extending from the emitter side of the base to said region of the base at a locus from the emitter between said one base electrode and said other base electrode, and said thickening portion being substantially isolated electrically firom said other base electrode when said face is contacted by space charge in said region and being of such extent outward from said region that electrical conductivity is substantially unaltered between said one electrode of the base and the emitter.

4. A transistorcomprising a base, an emitter and a collector mounted in opposed positions with respect to each other on opposite sides of said base and provided with electrodes for connection in an electric circuit, a pair of base electrodes for connecting said base to a pair of independent electric circuits for controlling the emitter current, one of the electrodes of said pair being spaced a shorter distance from the emitter than the other electrode of the pair, and a pair of ring-shaped auxiliary collectors each on an individually corresponding one of said opposite sides of said base and having opposed positions with respect to each other wherein one of said ringshaped auxiliary collectors surrounds said collector and the other of said ring-shaped auxiliary collectors surrounds said emitter and is located between said base electrodes, said auxiliary ring-shaped collectors being electrically connected to said collector outside said base, said base interconnecting in electrically conductive relation said base electrodes with said emitter and having on the emitter side of the base a portion opposite said collector supporting said one of said base electrodes and the emitter, and said base having a region adjacent to said collector and said auxiliary collectors electrically between said other electrode of the base and said emitter for said region to accommodate space charge produced in response to application of a predetermined potential to said collector and the auxiliary collectors thus altering the electrical resistance of said region, said portion of the base having a face against said one of said auxiliary collectors corresponding to the emitter side of the base and said face extending from the emitter side of the base to said region of the base, and said portion being substantially isolated electrically from said other base electrode when said face is contacted by space charge in said region and being of such extent from said region that electrical conductivity is substantially unaltered between said one electrode of the base and the emitter.

5. A transistor as recited in claim 4, wherein said base electrodes are of ring shape and surround said emitter.

6. A transistor comprising a base, an emitter and a collector mounted in opposed positions with respect to each other on opposite sides of said base and provided with electrodes for connection in an electric circuit, and a pair of base electrodes for connecting said base to a pair of independent electric circuits for controlling the emitter current, said base interconnecting in electrically conductive relation said base electrodes with said emitter and having on the emitter side of the base a portion opposite said collector supporting one of said base electrodes and the emitter, and said base having a region adjacent to said collector electrically between said other electrode of the base and said emitter for said region to accommodate space charge produced in response to application of a predetermined potential to said collector thus altering the electrical resistance of said region, said portion of the base having a relatively high impurity content as compared with said region of the base and having a face extending from the emitter side of the base to said region at a locus from the emitter between said one base electrode and said other base electrode, and said portion being substantially isolated electrically from said other base electrode when said face is contacted by space charge in said region and being of such extent from said region that electrical conductivity is substantially unaltered between said one electrode of the base and the emitter.

References Cited in the file of this patent UNITED STATES PATENTS 2,754,431 Johnson July 10, 1956 2,801,348 Pankove July 30, 1957 2,870,345 Overbeek Jan. 20, 1959 2,889,499 Rutz June 2, 1959 2,900,531 Wallmark Aug. 18, 1959 2,915,647 Ebers et al Dec. "1, 1959 

